Filter media including glass fibers

ABSTRACT

The present disclosure generally relates to filter media including glass fibers. The fiber characteristics (e.g., composition, dimensions) are selected to impart the desired solubility, filtration and mechanical properties so that the filter media may be used in the desired application.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/976,132, filed Dec. 22, 2010, which is incorporated herein byreference in its entirety.

FIELD OF INVENTION

Aspects described herein relate generally to filter media that compriseglass fibers and which exhibit desirable properties.

BACKGROUND

Filter media can be used to remove contamination in a variety ofapplications. The media can include a web of fibers. The fiber webprovides a porous structure that permits fluid (e.g., gas, air) to flowthrough the filter media. Contaminant particles contained within thefluid may be trapped on the fiber web.

The fiber characteristics (e.g., composition, dimensions) and filtermedia characteristics (e.g., basis weight, pore size, thickness) canaffect the filtration properties (e.g., efficiency, resistance to fluidflow through the media) and mechanical properties (e.g., tensileproperties, flex properties) of the media. Depending on the applicationin which the filter media is used, the media may be designed to meetcertain filter property and/or mechanical property requirements.

The filter media fiber can be formed of a variety of materials includingglass. In certain filter media applications, humans may be exposed toglass fiber fragments (e.g., one or more fibers, portions of fibers)which may be separated from the filter media during use. For example,such fiber fragments may be inhaled by humans and introduced into thebody. For health and safety reasons, it can be preferable for the glassfibers to be soluble in biological fluids, particularly when there is arisk of such exposure. These fibers may dissolve, completely or in part,when present in the body, thus, reducing the risk of health and safetyproblems which may otherwise arise.

However, when forming filter media from glass fibers that exhibitbiosoluble properties, it is important and can be challenging to meetthe filtration and mechanical property requirements for certainapplications in which the media is used.

SUMMARY OF THE INVENTION

Filter media as well as related components and methods are describedherein.

In one aspect, a filter media is provided. The filter media comprises afiber web. The fiber web includes a plurality of glass fibers having anaverage diameter of less than about 3.0 microns and a BaO contentgreater than about 7.2 wt %.

In another aspect, a plurality of glass fibers is provided. The glassfibers have an average diameter of less than about 3 microns and a BaOcontent of greater than about 7.2 wt %.

In a further aspect, a filter media is provided. The filter mediacomprises a fiber web that includes a plurality of glass fibers having aBaO content of greater than about 7.2 wt % and an alumina content ofless than about 3.0 wt %.

In yet another aspect, a filter media is provided. The filter mediaincludes a fiber web. The fiber web includes a plurality of glass fibershaving a BaO content of greater than about 7.2 wt %, a total alkalioxide content of greater than about 10.0 wt %, and a total alkalineearth oxide content of less than about 20.0 wt %.

In a different aspect, a method of filtering a fluid is provided. Themethod includes flowing a fluid through a filter media comprising afiber web. The fiber web includes a plurality of glass fibers having anaverage diameter of less than about 3.0 microns and a BaO contentgreater than about 7.2 wt %.

Other aspects, embodiments, advantages and features of the inventionwill become apparent from the following detailed description.

DETAILED DESCRIPTION

The present disclosure generally relates to filter media including glassfibers. As described further below, the fiber characteristics (e.g.,composition, dimensions) are selected to impart the filter media withdesired properties which can include biosoluble characteristics, as wellas excellent mechanical and filtration properties. In embodiments inwhich the glass fibers exhibit biosoluble characteristics, they may bedissolved, at least to some extent, in certain body fluids. This reducesthe risk of health and safety problems which otherwise may result fromthe presence of glass fibers in the body. Consequently, filter mediamade from such glass fibers may be particularly useful in applicationsthat involve some risk of human exposure to glass fiber fragments thatmay be separated from the media. It should also be understood that, insome embodiments, the glass fibers described herein may be useful inapplications other than filtration, for example, insulationapplications, such as cryogenic insulation.

In general, the filter media includes a plurality of fibers which areassembled together in a fiber web. The fiber webs described hereininclude glass fibers, though it should also be understood that otherfiber types may also be present including polymeric fibers andcellulosic fibers. In general, glass fibers constitute the majority (byweight) of the fibers in the fiber web. In some cases, more than onetype of glass fiber may be used. When more than one glass fiber type ispresent in the filter media, each of the glass fiber types may havecharacteristics (e.g., composition, dimensions) described herein; or, insome cases, one (or more) of the glass fiber types may havecharacteristics described herein and one (or more) of the glass fibertypes may have characteristics (e.g., composition, dimensions) that arenot described herein.

The composition of the glass fibers may be selected to impart desiredproperties including biosoluble characteristics. The glass fibersgenerally comprise silica (SiO₂) and one or more of the followingcompounds: barium oxide (BaO), alumina (Al₂O₃), alkali oxide(s) (e.g.,Li₂O, Na₂O, K₂O), alkaline earth oxide(s) (e.g., BeO, MgO, CaO, BaO),zinc oxide (ZnO) and boron oxide (B₂O₃). It should be understood thatnot each of these compounds is present in the glass fibers in everyembodiment, though typically the fibers include a mixture of at leastseveral of these compounds.

In certain embodiments, the glass fibers comprise BaO which may beimportant in imparting biosoluble characteristics and suitablemechanical properties (e.g., tensile strength, tensile elongation) tothe fibers. In some embodiments, the glass fibers have a BaO content ofgreater than about 7.2 wt %, greater than about 7.3 wt %, greater thanabout 7.4 wt %, greater than about 7.5 wt %, greater than about 7.6 wt%, greater than about 7.7 wt %, greater than about 7.8 wt %, greaterthan about 7.9 wt %, etc.; in some embodiments, greater than about 8.0wt %, greater than about 8.1 wt %, greater than about 8.2 wt %, greaterthan about 8.3 wt %, greater than about 8.4 wt %, or greater than about8.5 wt %; in some embodiments, greater than about 9.0 wt %, or greaterthan about 9.5 wt %; and, in some embodiments, greater than about 10.0wt %, or greater than about 10.5 wt %. In some embodiments, the BaOcontent may be less than about 25.0 wt %; less than about 20.0 wt %;less than about 15.0 wt %; or less than about 10.0 wt %. It should beunderstood that the glass fibers may have a BaO content within any ofthe above-noted upper and lower limits. For example, glass fibers mayhave a BaO content between about 7.2 wt % and about 25.0 wt %, betweenabout 7.3 wt % and about 25.0 wt %, between about 7.4 wt % and about25.0 wt %, between about 7.5 wt % and about 25.0 wt %, between about 7.6wt % and about 25.0 wt %, between about 7.7 wt % and about 25.0 wt %,between about 7.8 wt % and about 25.0 wt %, between about 7.9 wt % andabout 25.0 wt %, etc. Glass fibers may also have a BaO content betweenabout 8.0 wt % and about 25.0 wt %, between about 8.1 wt % and about25.0 wt %, between about 8.2 wt % and about 25.0 wt %, between about 8.3wt % and about 25.0 wt %, between about 8.4 wt % and about 25.0 wt %,between about 8.5 wt % and about 25.0 wt %, between about 8.0 wt % andabout 20.0 wt %, between about 8.0 wt % and about 15.0 wt %, betweenabout 8.0 wt % and about 10.0 wt %, etc.).

It should be understood that the BaO content may be outside theabove-noted ranges, in some embodiments.

In some embodiments, the glass fibers comprise alumina which may beimportant in imparting biosoluble characteristics and suitablemechanical properties. In some cases, the alumina content in the glassfibers may be greater than about 0.5 wt %; in some cases, greater thanabout 1.0 wt %; in some cases, greater than about 1.5 wt %; in somecases, greater than about 2.0 wt %; in some cases, greater than about2.5 wt %; in some cases, greater than about 3.0 wt %; in some cases,greater than about 4.0 wt %; in some cases, greater than about 5.0 wt %;and in some cases, greater than about 5.5 wt % The glass fibers may havean alumina content of less than about 10 wt %; in some embodiments, lessthan about 9.0 wt %; in some embodiments, less than about 8.0 wt %; insome embodiments, less than about 7.0 wt %; in some embodiments, lessthan about 6.0 wt %; in some embodiments, less than about 5.0 wt %; insome embodiments, less than about 4.0 wt %; in some embodiments, lessthan about 3.5 wt %; in some embodiments, less than about 3.0 wt %; insome embodiments, less than about 2.5 wt %. It should be understood thatthe glass fibers may have an alumina content within any of theabove-noted upper and lower limits (e.g., between about 0.5 wt % andabout 10.0 wt %, between about 0.5 wt % and about 6.0 wt %, betweenabout 0.5 wt % and about 3.0 wt %, between about 2.0 wt % and about 6.0wt %, between about 5.0 wt % and about 6.0 wt %, between about 1.0 wt %and about 2.5 wt %, etc).

It should be understood that the alumina content may be outside theabove-noted ranges, in some embodiments.

In general, the glass fibers may include one or more alkali oxide(s).For example, the presence of an alkali oxide may facilitate aspects ofprocessing such as enabling lower melt temperatures. Examples of alkalioxides include Li₂O, Na₂O, K₂O, Rb₂O, and Cs₂O. In some cases, Na₂Oand/or K₂O may be preferred alkali oxides. In some embodiments, theglass fibers have a total alkali oxide content (i.e., the content of allalkali oxides present added together) of greater than about 6.0 wt %; insome embodiments, greater than about 8.0 wt %; in some embodiments,greater than about 10.0 wt %; in some embodiments, greater than about12.0 wt %; and, in some embodiments, greater than about 15.0 wt %. Insome embodiments, the glass fibers have a total alkali oxide content ofless than about 25.0 wt %; in some embodiments, less than about 20.0 wt%; in some embodiments, less than about 15.0 wt %; and, in someembodiments, less than about 12.0 wt %. It should be understood that theglass fibers may have an alkali oxide content within any of theabove-noted upper and lower limits (e.g., between about 6.0 wt % andabout 25.0 wt %, between about 8.0 wt % and about 20.0 wt %, betweenabout 10.0 wt % and about 15.0 wt %, etc).

It should be understood that the alkali oxide content may be outside theabove-noted ranges, in some embodiments.

As noted above, Na₂O may be a preferred alkali oxide for use in theglass fibers. In some embodiments, the glass fibers have a Na₂O contentof greater than about 6.0 wt %; in some embodiments, greater than about8.0 wt %; in some embodiments, greater than about 9.0 wt %; in someembodiments, greater than about 10.0 wt %; in some embodiments, greaterthan about 12.0 wt %; and, in some embodiments, greater than about 15.0wt %. In some embodiments, the glass fibers have a Na₂O content of lessthan about 25.0 wt %; in some embodiments, less than about 20.0 wt %; insome embodiments, less than about 15.0 wt %; in some embodiments, lessthan about 12.0 wt %; in some embodiments, less than about 11.0 wt %;and, in some embodiments, less than about 10.0 wt %. It should beunderstood that the glass fibers may have a Na₂O content within any ofthe above-noted upper and lower limits (e.g., between about 6.0 wt % andabout 25.0 wt %, between about 8.0 wt % and about 20.0 wt %, betweenabout 9.0 wt % and about 15.0 wt %, between about 10.0 wt % and about11.0 wt %, etc).

It should be understood that the Na₂O content may be outside theabove-noted ranges, in some embodiments.

As noted above, K₂O may be a preferred alkali oxide for use in the glassfibers. The glass fibers may have a K₂O content of greater than about0.5 wt %; in some embodiments, greater than about 1.0 wt %; in someembodiments, greater than about 1.2 wt %; in some embodiments, greaterthan about 1.4 wt %; in some embodiments, greater than about 1.5 wt %;and, in some embodiments, greater than about 1.6 wt %. In someembodiments, the glass fibers have a K₂O content of less than about 8.0wt %; in some embodiments, less than about 5.0 wt %; in someembodiments, less than about 3.0 wt %; in some embodiments, less thanabout 2.0 wt %; in some embodiments, less than about 1.8 wt %; in someembodiments, less than about 1.7 wt %; in some embodiments, less thanabout 1.6 wt %; and, in some embodiments, less than about 1.5 wt %. Itshould be understood that the glass fibers may have a K₂O content withinany of the above-noted upper and lower limits (e.g., between about 0.5wt % and about 8.0 wt %, between about 1.0 wt % and about 3.0 wt %,between about 1.5 wt % and about 2.0 wt %, etc).

It should be understood that the K₂O content may be outside theabove-noted ranges, in some embodiments.

The glass fibers may also include one or more alkaline earth oxide(s).Examples of alkaline earth oxides include BeO, MgO, CaO, SrO and BaO. Inaddition to BaO, described above, MgO and/or CaO may be preferredalkaline earth oxides. In some embodiments, the glass fibers have atotal alkaline earth oxide content (i.e., the content of all alkalineearth oxides added together) of greater than about 6.0 wt %; in someembodiments, greater than about 8.0 wt %; in some embodiments, greaterthan about 10.0 wt %; and, in some embodiments, greater than about 12.0wt %. The total alkaline earth oxide content may be less than about 25.0wt %; in some cases, less than about 20.0 wt %; in some cases, less thanabout 15.0 wt %; and, in some embodiments, less than about 13.0 wt %. Itshould be understood that the glass fibers may have an alkaline earthoxide content within any of the above-noted upper and lower limits(e.g., between about 6.0 wt % and about 25.0 wt %, between about 8.0 wt% and about 20.0 wt %, between about 10.0 wt % and about 15.0 wt %,etc).

It should be understood that the alkaline earth oxide content may beoutside the above-noted ranges, in some embodiments.

In some embodiments, the glass fibers may have a MgO content of greaterthan about 0.1 wt %; in some embodiments, greater than about 0.2 wt %;in some embodiments, greater than about 0.3 wt %; in some embodiments,greater than about 0.4 wt %; and in some embodiments, greater than about0.5 wt %. In some embodiments, the glass fibers have a MgO content ofless than about 8.0 wt %; in some embodiments, less than about 5.0 wt %;in some embodiments, less than about 3.0 wt %; in some embodiments, lessthan about 2.0 wt %; in some embodiments, less than about 1.0 wt %; insome embodiments, less than about 0.8 wt %; in some embodiments, lessthan about 0.6 wt %; in some embodiments, less than about 0.5 wt %; and,in some embodiments, less than about 0.4 wt %. It should be understoodthat the glass fibers may have a MgO content within any of theabove-noted upper and lower limits (e.g., between about 0.1 wt % andabout 8.0 wt %, between about 0.2 wt % and about 2.0 wt %, between about0.3 wt % and about 1.0 wt %, between about 0.4 wt % and about 0.6 wt %,etc).

It should be understood that the MgO content may be outside theabove-noted ranges, in some embodiments.

The glass fibers may have a CaO content of greater than about 0.1 wt %;in some embodiments, greater than about 0.5 wt %; in some embodiments,greater than about 1.0 wt %; in some embodiments, greater than about 1.5wt %; in some embodiments, greater than about 1.8 wt %; and in someembodiments, greater than about 2.0 wt %. In some embodiments, the glassfibers have a CaO content of less than about 15.0 wt %; in someembodiments, less than about 10.0 wt %; in some embodiments, less thanabout 5.0 wt %; in some embodiments, less than about 4.0 wt %; in someembodiments, less than about 3.0 wt %; in some embodiments, less thanabout 2.5 wt %; in some embodiments, less than about 2.2 wt %; in someembodiments, less than about 2.1 wt %; and, in some embodiments, lessthan about 2.0 wt %. It should be understood that the glass fibers mayhave a CaO content within any of the above-noted upper and lower limits(e.g., between about 0.1 wt % and about 15.0 wt %, between about 1.0 wt% and about 10.0 wt %, between about 1.5 wt % and about 5.0 wt %,between about 1.8 wt % and about 2.2 wt %, etc).

It should be understood that the CaO content may be outside theabove-noted ranges, in some embodiments.

In some embodiments, the glass fibers may include ZnO. In some cases,the ZnO content in the glass fibers is greater than about 1.5 wt %; insome cases, greater than about 2.0 wt %; in some cases, greater thanabout 2.5 wt %; in some cases, greater than about 3.0 wt %; in somecases, greater than about 3.5 wt %; and in some cases, greater thanabout 4.0 wt %. The ZnO content may be less than about 8.0 wt %; in somecases, less than about 6.0 wt %; in some cases, less than about 5.0 wt%; in some cases, less than about 4.5 wt %; in some cases, less thanabout 4.0 wt %; and, in some embodiments, less than about 3.5 wt %. Itshould be understood that the glass fibers may have a ZnO content withinany of the above-noted upper and lower limits (e.g., between about 1.5wt % and about 8.0 wt %, between about 2.5 wt % and about 6.0 wt %,between about 2.5 wt % and about 5.0 wt %, between about 3.0 wt % andabout 4.5 wt %, etc).

It should be understood that the ZnO content may be outside theabove-noted ranges, in some embodiments.

The glass fibers may include B₂O₃. In some cases, the B₂O₃ content inthe glass fibers may be greater than about 5.0 wt %; in some cases,greater than about 8.0 wt %; in some cases, greater than about 9.0 wt %;in some cases, greater than about 10.0 wt %; and, in some cases, greaterthan about 11.0 wt %. The B₂O₃ content may be less than about 15.0 wt %;less than about 13.0 wt %; less than about 12.0 wt %; and, in someembodiments, less than about 11.0 wt %. It should be understood that theglass fibers may have a B₂O₃ content within any of the above-noted upperand lower limits (e.g., between about 5.0 wt % and about 15.0 wt %,between about 8.0 wt % and about 13.0 wt %, between about 10.0 wt % andabout 12.0 wt %, etc).

It should be understood that the B₂O₃ content may be outside theabove-noted ranges, in some embodiments.

As described above, generally, the glass fibers include a suitableamount of silica. Silica generally is the major component by weight inthe glass fibers. For example, the silica content may be greater thanabout 45.0 wt %; in some cases, greater than about 50.0 wt %; in somecases, greater than about 55.0 wt %; in some cases, greater than about60.0 wt %; and, in some cases, greater than about 65.0 wt %. The silicacontent may be less than about 80.0 wt %; in some cases, less than about75.0 wt %; in some cases, less than about 65.0 wt %; and, in some cases,less than about 55.0 wt %. It should be understood that the glass fibersmay have a silica content within any of the above-noted upper and lowerlimits (e.g., between about 45.0 wt % and about 80.0 wt %, between about55.0 wt % and about 70.0 wt %, between about 60.0 wt % and about 65.0 wt%, etc).

It should be understood that the silica content may be outside theabove-noted ranges, in some embodiments.

It should be understood that the glass fibers may include anycombination of the above-described components within any of the suitableweight contents that are described above. For example, the fibers mayinclude a BaO content of greater than about 7.2 wt % (or 7.3 wt % or 7.4wt % or 7.5 wt % or 7.6 wt % or 7.7 wt % or 7.8 wt % or 7.9 wt % or 8.0wt %, etc.) of the fiber web and an alumina content of less than about3.0 wt %; and, in some embodiments, the glass fibers may include a BaOcontent of greater than about 7.2 wt % (or 7.3 wt % or 7.4 wt % or 7.5wt % or 7.6 wt % or 7.7 wt % or 7.8 wt % or 7.9 wt % or 8.0 wt %, etc.),a total alkali oxide content of greater than about 10.0 wt % and analkaline earth oxide content of less than about 20.0 wt %; etc. Inanother example, the glass fibers may include a BaO content of betweenabout 7.2 wt % (or 7.3 wt % or 7.4 wt % or 7.5 wt % or 7.6 wt % or 7.7wt % or 7.8 wt % or 7.9 wt % or 8.0 wt %, etc.) and about 25.0 wt %, analumina content of between about 0.5 wt % and about 10.0 wt %; a totalalkali oxide content of between about 6.0 wt % and about 25.0 wt %, atotal alkaline earth oxide content of between about 6.0 wt % and about25.0 wt %, a ZnO content of between about 1.5 wt % and about 8.0 wt %, aB₂O₃ content of between about 5.0 wt % and about 15.0 wt %, and a silicacontent of between about 45.0 wt % and about 80.0 wt %, etc. In yetanother example, the glass fibers may include a BaO content of betweenabout 7.2 wt % (or 7.3 wt % or 7.4 wt % or 7.5 wt % or 7.6 wt % or 7.7wt % or 7.8 wt % or 7.9 wt % or 8.0 wt %, etc.) and about 20.0 wt %, analumina content of between about 1.0 wt % and about 2.5 wt %, a totalalkali oxide content of between about 10.0 wt % and about 15.0 wt %, atotal alkaline earth oxide content of between about 10.0 wt % and about15.0 wt %, a ZnO content of between about 3.0 wt % and about 4.5 wt %, aB₂O₃ content of between about 10.0 wt % and about 12.0 wt %, and asilica content of between about 60.0 wt % and about 65.0 wt %, etc.

For some embodiments, the glass fibers may include a BaO content ofbetween about 7.2 wt % (or 7.3 wt % or 7.4 wt % or 7.5 wt % or 7.6 wt %or 7.7 wt % or 7.8 wt % or 7.9 wt % or 8.0 wt %, etc.) and about 25.0 wt%, an alumina content of between about 0.5 wt % and about 10.0 wt %; aNa₂O content of between about 6.0 wt % and about 25.0 wt %, a K₂Ocontent of between about 0.5 wt % and about 8.0 wt %, a MgO content ofbetween about 0.1 wt % and about 8.0 wt %, a CaO content of betweenabout 0.1 wt % and about 15.0 wt %, a ZnO content of between about 1.5wt % and about 8.0 wt %, a B₂O₃ content of between about 5.0 wt % andabout 15.0 wt %, and a silica content of between about 45.0 wt % andabout 80.0 wt %, etc. For example, the glass fibers may include a BaOcontent of between about 7.2 wt % and about 20.0 wt %, an aluminacontent of between about 1.0 wt % and about 2.5 wt %, a Na₂O content ofbetween about 10.0 wt % and about 11.0 wt %, a K₂O of between about 1.5wt % and about 2.0 wt %, a MgO content of between about 0.4 wt % andabout 0.6 wt %, a CaO content of between about 1.8 wt % and about 2.2 wt%, a ZnO content of between about 3.0 wt % and about 4.5 wt %, a B₂O₃ ofbetween about 10.0 wt % and about 12.0 wt %, and a silica content ofbetween about 60.0 wt % and about 65.0 wt %, etc.

It should be understood that the glass fibers may be analyzed usingInductively Coupled Plasma Spectrophotography (ICP) analysis, asperformed according to Battery Council International (BCI) ProcedureXIIB, to determine their composition including the weight percentage ofeach component.

In general, the glass fibers used in the filter media described hereinmay have any suitable dimensions. In some embodiments, the glass fibershave an average diameter of less than about 10.0 microns. In some cases,it may be preferred for the glass fibers to have an average diameter ofless than about 3.0 microns. In some cases, the glass fibers have anaverage diameter of less than about 2.0 microns, less than about 1.5microns, less than about 1.0 micron, or less than about 0.5 microns. Theaverage diameter of the glass fibers may be greater than about 0.1microns; in some embodiments, greater than about 0.5 microns; in someembodiments, greater than about 1.0 microns; in some embodiments,greater than about 1.5 microns; and, in some embodiments, greater thanabout 2.0 microns. It should be understood that the glass fibers mayhave an average diameter within any of the above-noted upper and lowerlimits (e.g., between about 0.1 microns and about 3.0 microns, etc.).

The glass fibers may vary in length as a result of process variations.The aspect ratios (length to diameter ratio) of the glass fibers may begenerally in the range of about 10 to about 10,000. In some embodiments,the aspect ratio of the glass fibers may be in the range of about 100 toabout 2500; or, in the range of about 200 to about 1000; or, in therange of about 300 to about 600. In some embodiments, the average aspectratio of the glass fibers may be about 1,000; or about 300. It should beappreciated that the above-noted dimensions are not limiting and thatthe glass fibers may also have other dimensions.

In some embodiments, the average length of glass fibers in a filtermedia may generally be between about 0.1 mm and about 5.0 mm, or forexample, between about 2 mm and about 4 mm. It should be appreciatedthat the above-noted dimensions are not limiting and that the glassfibers may also have other dimensions.

The glass fibers may have a suitable surface area as measured throughBET Surface Area Analysis (SSA) in accordance with method number 8(Surface Area) of Battery Council International Standard BCIS-03A (2009revision), “BCI Recommended Test Methods VRLAAGM Battery Separators.”With this technique, the BET surface area is measured via an adsorptionanalysis using a BET surface analyzer (e.g., Micromeritics Gemini II2370 Surface Area Analyzer) with nitrogen gas. The sample amountmeasured is between 0.5 and 0.6 grams in a ¾ inch tube; and, the sampleis allowed to degas at 75° C. for a minimum of 3 hours.

In some embodiments, the surface area of the glass fibers may be greaterthan about 0.1 m²/g, greater than about 0.5 m²/g, greater than about 1.0m²/g, greater than about 1.5 m²/g, greater than about 2.0 m²/g, greaterthan about 3.0 m²/g, greater than about 4.0 m²/g, greater than about 5.0m²/g, greater than about 6.0 m²/g, or greater than about 6.5 m²/g. Insome cases, the surface of the glass fibers may range between about 0.1m²/g and about 10.0 m²/g, between about 0.1 m²/g and about 8.5 m²/g,between about 0.1 m²/g and about 6.5 m²/g, between about 0.1 m²/g andabout 3.0 m²/g, or between about 0.1 m²/g and about 2.8 m²/g

The glass fibers may be any suitable kind of glass fiber. For example,the glass fibers can be microglass fibers. Microglass fibers are drawnfrom bushing tips and further subjected to flame blowing or rotaryspinning processes. In some cases, microglass fibers may be made using aremelting process. In some embodiments, the glass fibers can includechopped strand glass fibers.

In addition to the fibers described above, the filter media may includea binder. In some embodiments, a binder coats the glass fibers, adheringfibers to each other and facilitating adhesion between the fibers. Abinder that adheres fibers together may have any suitable compositionand may be provided as any suitable percentage of the filter media. Insome embodiments, a binder of the filter media may include polyester,polyolefin, polyurethane, polyvinyl acetate, polyvinyl alcohol,polyacrylic acid, acrylic, styrene, styrene acrylic, or combinationsthereof. The filter media may include an amount of binder between about0 wt % and about 20 wt %, between about 1 wt % and about 19 wt %,between about 1 wt % and about 10 wt %, or between about 2 wt % andabout 5 wt %, etc.

The filter media may also include a variety of other suitable additives(typically, in small weight percentages) such as, fluorocarbon polymer,surfactants, coupling agents, and crosslinking agents, amongst others.The media may also include other components such as a substrate,additional fiber webs, binder materials and the like.

As discussed above, for some cases, such as for health and safetyreasons, it may be beneficial for filter media to exhibit biosolubleproperties. The degree of biosolubility of the glass fibers in the mediamay be determined by measuring Kdis which is an assessment of the rateof fiber dissolution in ng/hour/cm². Kdis may be measured by immersing0.25 grams of the fibers for 28 days in a physiological fluid (e.g.,Gamble fluid) at a temperature of 37° C. and at a flow rate of 0.25mL/min. Fibers are held in a thin layer between 0.4 micron polycarbonatemembranes supported by a plastic support mesh and the assembly is placedwithin a polycarbonate sample cell through which fluid may percolate.The pH of the fluid is maintained to be 7.4+/−0.2 (e.g., through the useof a 5% CO₂ and 95% N₂ positive pressure bubbled through the fluid).Weight losses are measured using ICP collected at specified timeintervals (e.g., once per week). The total weight loss is calculatedbased on the difference between the final and initial weight of thefiber sample. As a control for test accuracy, reference fibers withknown Kdis values are also measured. Kdis values are calculated based onthe following formula:

Kdis=[d ₀ρ(I−(M/M ₀)^(0.5)])/2t

where d₀ is the initial fiber diameter, ρ is the initial density of thefiber, M₀ is the initial mass of the fibers, M the final mass of thefibers, and t is the time over which the measurement was made.

In some embodiments, the glass fibers have a Kdis of greater than about85 ng/hour/cm²; in some embodiments, the Kdis may be greater than about90 ng/hour/cm²; in some embodiments, the Kdis may be greater than about95 ng/hour/cm²; in some embodiments, the Kdis may be greater than about100 ng/hour/cm²; in some embodiments, the Kdis may be greater than about110 ng/hour/cm²; in some embodiments, the Kdis may be greater than about115 ng/hour/cm²; in some embodiments, the Kdis may be greater than about130 ng/hour/cm²; and, in some embodiments, the Kdis may be greater thanabout 150 ng/hour/cm². Further, the glass fibers may have a Kdis ofbetween about 85 ng/hour/cm² and about 200 ng/hour/cm², between about 90ng/hour/cm² and about 150 ng/hour/cm², between about 95 ng/hour/cm² andabout 130 ng/hour/cm², or between about 100 ng/hour/cm² and about 110ng/hour/cm².

In general, the filter media can have varying basis weights, pore sizes,thicknesses, permeabilities, dirt holding capacities, efficiencies, andpressure drops, depending upon the requirements of a desiredapplication. Representative values and ranges for some of thesecharacteristics are provided in the following paragraphs. However, itshould be understood that these values and ranges are not limiting andthat certain embodiments may not have values and ranges outside thosedescribed below. It should also be understood that though values andranges are provided for filter media, the same values and ranges mayapply to fiber web(s) described herein.

In general, the filter media may have any suitable basis weight. Forexample, basis weight of the filter media may range from between about 5grams per square meter (gsm) and about 1000 gsm, between about 25 gsmand about 150 gsm, or between about 55 gsm and about 85 gsm, etc. Thebasis weight of the filter media is measured according to the TechnicalAssociation of the Pulp and Paper Industry (TAPPI) Standard T410.

The filter media may generally have any suitable thickness. Suitablethicknesses of the filter media may include, but are not limited to,between about 0.05 mm and about 100.0 mm, between about 0.10 mm andabout 10.0 mm, between about 0.20 mm and about 0.90 mm, or between about0.25 mm and about 0.50 mm, etc. Thickness is determined according toTAPPI T411 using an appropriate caliper gauge (e.g., electronic ormechanical microgauge, tested at 7.3 psi load).

In general, the filter media may exhibit excellent mechanical properties(e.g., tensile, flex properties) that enable it to be used in thedesired application. Mechanical properties can be measured in terms ofmachine direction and cross-machine direction which have usual meaningsin the art. That is, a machine direction is referred to as a directionin which the fiber web moves along the machine during processing. Across-machine direction is referred to as a direction perpendicular tothe machine direction.

In some embodiments, the tensile strength of the filter media in themachine direction may be greater than about 5 inches/lb, greater thanabout 6 inches/lb; or in some cases, greater than about 7 inches/lb. Forexample, the tensile strength of the filter media in the machinedirection may range between about 5 inches/lb and about 20 inches/lb, orbetween about 7 inches/lb and about 10 inches/lb, etc. The tensilestrength of the filter media in the cross-machine direction may begreater than about 2 inches/lb; and, in some cases, greater than about 4inches/lb. In some embodiments, the tensile strength of the filter mediain the cross-machine direction may range between about 2 inches/lb andabout 20 inches/lb, or between about 4 inches/lb and about 10 inches/lb,etc.

The tensile elongation of the filter media in the machine direction maybe greater than about 0.8%; and, in some cases, greater than about 1.0%.For example, the tensile elongation of the filter media in the machinedirection may be between about 0.8% and about 5.0%, and, in some cases,between about 1.0% and about 3.0%, etc. The tensile elongation of thefilter media in the cross-machine direction may be greater than about1.5%; and, in some cases, greater than about 1.8%. In some embodiments,the tensile elongation of the filter media in the cross-machinedirection may be between about 1.5% and about 8.0%, between about 1.8%and about 5.0%, and, in some cases, between about 2.0% and about 3.0%,etc.

Tensile strength and elongation are measured following TAPPI T 1009“Tensile strength and elongation at break.”

In some embodiments, the flex tensile strength of the filter media inthe machine direction may be greater than about 2.0 inches/lb, greaterthan about 3.0 inches/lb, or greater than about 3.5 inches/lb. Forexample, the flex tensile strength of the filter media in the machinedirection may be between about 1.0 inches/lb and about 10.0 inches/lb,in some cases, between about 2.0 inches/lb and about 8.0 inches/lb, and,in some cases, between about 3.5 inches/lb. and about 5.0 inches/lb,etc. The flex tensile elongation of the filter media in the machinedirection may be greater than about 0.2%, greater than about 0.3%, orgreater than about 0.4%. In some embodiments, the flex tensileelongation of the filter media in the machine direction may rangebetween about 0.1% and about 5.0%, between about 0.2% and about 3.0%,and, in some cases, between about 0.4% and about 1.0%, etc.

The flex tensile strength and flex elongation of the filter media in themachine direction of the filter media was measured under a temperatureof 50° C. and a relative humidity of 90%, also known as humid agingconditions. When subject to humid aging conditions, the filter media mayadvantageously retain its tensile strength properties over time. Forexample, in some embodiments, after a 96 hour period subject to humidaging conditions, the flex tensile strength decreases by an amount lessthan about 50%; in some embodiments, the flex tensile strength decreasesby an amount less than about 40%; in some embodiments, the flex tensilestrength decreases by an amount less than about 30%; and in someembodiments, the flex tensile strength decreases by an amount, less thanabout 20%; in some embodiments, the flex tensile strength decreases byan amount between about 5% and about 50%; in some embodiments, the flextensile strength decreases by an amount between about 10% and about 40%,between 15% and about 30%, or between about 15% and about 20%. In someembodiments, after 96 hours subject to humid aging conditions, the flexelongation decreases by an amount less than about 40%; in someembodiments, the flex elongation decreases by an amount less than about30%; in some embodiments, the flex elongation decreases by an amountless than about 25%; in some embodiments, the flex elongation decreasesby an amount less than about 20%; in some embodiments, the flexelongation decreases by an amount between about 5% and about 40%; insome embodiments, the flex elongation decreases by an amount betweenabout 10% and about 30%; in some embodiments, the flex elongationdecreases by an amount between about 15% and about 25%; in someembodiments, the flex elongation decreases by an amount between about15% and about 20%. The flex tensile strength and flex elongation aremeasured according to TAPPI T 1010 “Flexibility Index of Fiber GlassMats.” In a flex tensile strength and flex elongation measurement, onesample of filter media is flexed 180 degrees over a ⅛ inch mandrel suchthat one of the samples is flexed wire to wire (upstream to upstreamside), the other sample is flexed felt to felt (downstream to downstreamside), and the average of measurements from the two samples is recorded.The load failure in measuring the flex tensile strength is determined ata 4 inch gauge length.

In some embodiments, the stiffness of the filter media in the machinedirection may be greater than about 500 mg; and in some cases, thestiffness is greater than about 600 mg. For example, the stiffness ofthe filter media in the machine direction may range between about 500 mgand about 2000 mg, between about 600 mg and about 1000 mg, or betweenabout 600 mg and about 800 mg. In some instances, the stiffness of thefilter media in the cross-machine direction may be greater than about150 mg; and, in some cases, greater than about 350 mg. In someembodiments, the stiffness of the filter media in the cross-machinedirection may range between about 150 mg and about 1500 mg, betweenabout 300 mg and about 800 mg, or between about 350 mg and about 500 mg.Stiffness of the filter media is measured according to TAPPI Standard T543.

In general, filter media described herein can be formed by any suitableprocess. To form the glass fibers, raw materials (e.g., particles ofBaO, silica, alumina, alkali oxides, alkaline earth oxides, ZnO, B₂O₃),can be mixed together and heated in a furnace (e.g., to a temperaturebetween 2400-2700° F.) so that the materials melt and form a homogeneousmixture. Once the materials are suitably combined together, the mixturemay be fiberized. In some embodiments, the mixture is melted and formedinto glass material (e.g., in the form of patties, marbles, pellets),which are then fiberized through a flame blown system.

In an exemplary embodiment of a flame blown system, a mixture of glassmaterial is heated to a temperature sufficient for the glass material toform a viscous melt. Using a suitable pulling guide system, the viscousmelt is then drawn into coarse glass filaments. The coarse glassfilaments are subsequently subjected to a high temperature gas jetflame, remelting the coarse glass filament to form fine glass fibers. Insome cases, the high temperature gas jet flame impinges upon the coarseglass filaments at generally a right angle to propel the resulting fineglass fibers through a forming tube. In some instances, the fine glassfibers may move through the forming tube via application of a vacuumsuction system and on to a collection area. In some embodiments,although not necessarily required, a binder may be applied to the fibers(e.g., via spray application) as they pass through the forming tubetoward the collection area. In the collection area, fibers may aggregateand entangle into a wool-like composition, which may then be weighed andbaled, as appropriate for further processing.

In an exemplary embodiment of a rotary system, the glass material ismixed together and melted in a furnace to form a viscous glass melt. Theviscous glass melt is introduced into a rotating spinner system. In someembodiments, a rotating spinner system includes a disc-like or bowl-likestructure having perforated sidewalls and the spinner appliescentrifugal forces to the glass melt so that the glass melt is extrudedthrough the openings in the sidewall. Melt streams that arise from theglass melt extrusion are cooled to form fibers that, at times, may besmaller in diameter than the diameters of the extrusion holes. In someembodiments, though not all, a rotary system may include a burner forheating of the interior of the rotating spinner and the glass meltinside the spinner. In some cases, an annular burner surrounding thespinner may supply exhaust gases for heating sidewalls of the spinnerand extruded streams of glass melt. Exhaust gases may also provideaerodynamic drag forces to assist in providing attenuation of the meltstreams into fine glass fibers. Further, in some embodiments, an annularcompressed air blower may be employed to provide aerodynamic attenuatingforces so as to fragment fibers into shorter lengths and controlmovement of the fibers as they leave the fiberizing system. In somecases, as discussed above, fibers may be subject to a gas jet. Fineglass fibers may also have binder or other suitable material(s) applied(e.g., sprayed) onto the fibers prior to collection on a conveyor beltor other suitable collection device. Upon collection, fibers may besuitably weighed and baled.

While glass fibers described herein may be prepared by a flame blownprocess or a rotary process, it should be appreciated that suitableglass fibers can be prepared by any appropriate method. The fine glassfibers may be formed in bulk, processed and incorporated into filtermedia.

The filter media may be produced using processes based on knowntechniques. For example, the filter media may be produced using a wetlaid process or a dry laid process.

In general, a wet laid process involves mixing together the fibers toprovide a glass fiber slurry. In some cases, the slurry is anaqueous-based slurry. If mixtures of fibers (e.g., glass and polymericfibers) are used, then the fibers may be processed through a pulperbefore being mixed together. In some embodiments, a combination ofmicroglass and chopped strand glass fibers may be included in the glassfiber slurry, though chopped strand glass fibers are not required. Itshould be understood that not all glass fibers in the filter media arerequired to have the compositions described above as some glass fibersmay have other suitable compositions.

It should be appreciated that any suitable method for creating a glassfiber slurry may be used. In some cases, additional additives are addedto the slurry to facilitate processing. The temperature may also beadjusted to a suitable range, for example, between 33° F. and 100° F.(e.g., between 50° F. and 85° F.). In some embodiments, the temperatureof the slurry is maintained. In some cases, the temperature is notactively adjusted.

In some embodiments, the wet laid process uses similar equipment as aconventional papermaking process, which includes a hydropulper, a formeror a headbox, a dryer, and an optional converter. For example, theslurry may be prepared in one or more pulpers. After appropriatelymixing the slurry in a pulper, the slurry may be pumped into a headbox,where the slurry may or may not be combined with other slurries oradditives may or may not be added. The slurry may also be diluted withadditional water such that the final concentration of fiber is in asuitable range, such as for example, between about 0.1% to 0.5% byweight.

In some cases, the pH of the glass fiber slurry may be adjusted asdesired. For instance, the pH of the glass fiber slurry may rangebetween about 1.5 and about 4.5, or between about 2.6 and about 3.2.

Before the slurry is sent to a headbox, the slurry may be passed throughcentrifugal cleaners for removing unfiberized glass or shot. The slurrymay or may not be passed through additional equipment such as refinersor deflakers to further enhance the dispersion of the fibers. Fibers maythen be collected on a screen or wire at an appropriate rate using anysuitable machine, e.g., a fourdrinier, a rotoformer, a cylinder, or aninclined wire fourdrinier.

In some embodiments, the process involves introducing binder (and/orother components) into a pre-formed glass fiber layer. In someembodiments, as the glass fiber layer is passed along an appropriatescreen or wire, different components included in the binder, which maybe in the form of separate emulsions, are added to the glass fiber layerusing a suitable technique. In some cases, each component of the binderresin is mixed as an emulsion prior to being combined with the othercomponents and/or glass fiber layer. In some embodiments, the componentsincluded in the binder may be pulled through the glass fiber layerusing, for example, gravity and/or vacuum. In some embodiments, one ormore of the components included in the binder resin may be diluted withsoftened water and pumped into the glass fiber layer.

In other embodiments, a dry laid process is used. In a dry laid process,glass fibers are chopped and dispersed in air that is blown onto aconveyor, and a binder is then applied. Dry laid processing is typicallymore suitable for the production of highly porous media includingbundles of glass fibers.

As previously indicated, the filter media disclosed herein can beincorporated into a variety of filter elements using known techniques.The filter elements may be used in various applications including, butnot limited to, air filtration applications (e.g., HEPA, ULPA, lowefficiency applications) and hydraulic filter media applications. Forexample, the filter media may be used in heating and/or air conditioningapplications. In some cases, the filter element may include a housingthat may be disposed around the filter media. The housing can havevarious configurations, with the configurations varying based on theintended application.

It should be understood that the filter media and filter elements mayhave a variety of different constructions and the particularconstruction depends on the application in which the filter media andelements are used.

EXAMPLES

The following three non-limiting examples describe filter media thatexhibit characteristics described herein including high Kdis, as well assuitable mechanical and filtration properties.

Glass fibers were manufactured by heating a mixture of appropriatecompounds in a furnace to melt the compounds forming a homogeneousblend. The blend was subsequently fiberized into one batch of fine glassfibers having an average diameter of 0.6 microns and a second batch ofglass fibers having an average diameter of 3.0 microns. The compositionsfor these glass fibers are shown in Table 1 below.

TABLE 1 Weight and Molar Percentages of Components in Glass Fibers forExamples 1-3. Exam- Exam- Exam- Exam- Exam- Exam- ple 1 ple 1 ple 2 ple2 ple 3 ple 3 (wt %) (mol %) (wt %) (mol %) (wt %) (mol %) SiO₂ 61.267.2 60.8 67.0 61 67.2 Al₂O₃ 2.1 1.4 2.4 1.6 1.3 0.8 CaO 2 2.3 2 2.3 22.3 MgO 0.4 0.7 0.5 0.8 0.4 0.7 B₂O₃ 10.5 9.9 11 10.4 10.5 10.0 K₂O 1.51.0 1.8 1.3 1.5 1.1 Na₂O 10.5 11.1 10 10.7 10 10.7 ZnO 3.4 2.8 2.5 2.0 43.2 BaO 8.4 3.6 9 3.9 9.3 4.0

Glass fiber webs were prepared from the above-described batches of glassfibers and chopped strand fibers (¼″ Deltachop 8610E DE fibers obtainedfrom Pittsburgh Plate and Glass Industries, Inc. having an average fiberdiameter of 6.5 microns). The fiber webs were prepared on a pilotmachine without resin binder and then saturated in the laboratory toproduce a filter media prior to testing. The weight percentages of theglass fiber components in the filter media were as follows: 61% byweight 0.6 micron fibers, 30% by weight 3.0 micron fibers, and 9% byweight chopped strand fibers. A resin binder formulation having a batchsize of 2500 mL with the composition provided in Table 2 was included inthe fiber web.

TABLE 2 Resin Binder Formula Material As Recorded (g) H2O 2433.3 Rohm &Haas Rhoplex E32NP 39.7 Rohm & Haas Resin HF-05A 17.6 Asahi GlassCompany Repearl F-35 9.4Prior to testing, samples were cured for 3 minutes at 150° C. The Kdisof the glass fibers from Examples 1-3 was measured according to themethods described above after 7 days, 16 days and 28 days, and thevalues are recorded in Table 3 below.

TABLE 3 Biosolubility Characteristics Measured of Glass Fibers forExamples 1-3. Example 1 Example 2 Example 3 28 16 7 28 16 7 28 16 7 daysdays days days days days days days days Kdis 93.2 82.7 85.9 99.2 95.4102.2 116.2 111.0 107.7

Mechanical properties of the filter media of Examples 1-3 were measuredand are recorded in Table 4. The test procedures noted above in theDetailed Description were used to measure the properties. Filtrationproperties of the filter media of Examples 1-3 were also measured andare recorded in Table 4.

Penetration through the filter media was measured as a ratio of theparticle concentration before passage through the filter and theparticle concentration after passage through the filter, in accordancewith ASTM Standard D2986. Two penetration tests were conducted. Onepenetration test involved blowing dioctyl phthalate (DOP) particles 0.3microns in size through a filter media at 5.3 cm/sec. and measuring thepercentage of particles that penetrate through the filter media. Theother penetration test followed the same procedure using DOP particles0.3 microns in size except traveling at a 2.5 cm/sec face velocity.Filter efficiency is defined as (100−Penetration %). Gamma provides arelationship between penetration and pressure drop across a filter, andis expressed according to the following:

gamma=(−log(Penetration %/100)/(pressure drop), mm H₂O)×100

The pressure drop across the filter media was measured using aresistance rig with no exposure to aerosol contaminants. The pressuredrop was measured as the difference in pressure across the filter mediaduring pure air flow through at a velocity of 5.3 centimeters persecond, using a digital manometer.

Loss on ignition (LOI %) was measured according to reference teststandard T1013 “Loss on Ignition of fiber glass mats.” The LOI testdetermines the fraction of filter media that is volatile and non-glasswhere the weight of a sample of filter media is measured before andafter being subjected to temperatures of 1000° F.+/−50° F. for a minimumof 2 minutes. The LOI % recorded in Table 4 is considered to be thebinder content of the filter media.

The AC Flex Light Weight (AC Flex Lt Wt) was measured using an AC FlexTester on a 2 inch by 4 inch sample cut with the 4 inch side aligned inthe machine direction. The sample was clamped in a specimen holder. Thetester was activated to cyclically flex the sample at a rate of 48cycles per minute (+/−1 cycle) using a flex weight of 413.2 grams. Thenumber of flex cycles until the specimen broke was recorded.

The water rise was measured according to MIL-STD-282 “Operation of theE1R3 Water-Repellency-Test Apparatus.” In this test, the filter media isrigidly supported on one side with a 20 cm² area on the opposite sideexposed to a water pressure that increases at a constant rate. The waterrepellency of the filter media is determined by the height of the watercolumn necessary to cause penetration of water through the filter media.

TABLE 4 Mechanical and Performance Characteristics Measured of the FiberWebs for Examples 1-3. Example 1 Example 2 Example 3 Machine DirectionTensile 7.43 6.81 5.30 Strength (inches/lb) Machine Direction Elongation(%) 1.16 1.19 0.93 Cross Direction Tensile 4.26 4.37 2.55 Strength(inches/lb) Cross Direction Elongation (%) 1.83 1.85 2.23 Flex TensileStrength (inches/lb) 3.58 3.38 2.70 Flex Elongation (%) 0.40 0.42 0.41Machine Direction Stiffness (mg) 644 576 500 Cross Direction Stiffness(mg) 364 280 196 Basis Weight (lb/ream) 43.5 40.3 40.1 50 kPa Caliper(inches) 0.0116 0.0107 0.0113 LOI (%) 5.6 5.9 6.0 ΔP, 5.3 cm/sec (mmH₂O) 40.7 32.4 32.5 DOP Penetration, 5.3 cm/sec (%) 0.0007 0.0070 0.0063DOP Penetration, 2.5 cm/sec (%) 0.000382 0.00728 0.00595 AC Flex Lt. Wt.(cycles) 10 12 8 Water Rise, ≈31 in./min. (inches 60.5 56.8 58.7 H₂O)Gamma 12.7 12.8 13.0

The flex tensile strength and flex tensile elongation properties of thefilter media of Examples 1-3 were measured at specific time incrementswhile exposed to humid aging conditions at a temperature of 50° C. and arelative humidity of 90%. The results of the measurements were recordedin Table 5. The results show that the glass fiber compositions describedherein may have a high Kdis and may be used to manufacture filter mediathat exhibit favorable mechanical and filtration properties.

TABLE 5 Flex Tensile and Flex Elongation Properties Measured of FiberWebs for Examples 1-3. As Is 24 hr 48 hr 72 hr 96 hr Flex TensileStrength Example 1 3.58 3.35 3.26 3.06 2.97 Example 2 3.38 2.93 2.992.68 2.47 Example 3 2.70 2.45 2.31 2.25 2.36 Flex Elongation Example 10.40 0.38 0.37 0.37 0.38 Example 2 0.42 0.38 0.39 0.36 0.32 Example 30.41 0.39 0.34 0.38 0.36

The above results are provided only as examples of suitable filter mediadescribed herein.

Having thus described several aspects of at least one embodiment of thisinvention, it is to be appreciated various alterations, modifications,and improvements will readily occur to those skilled in the art. Suchalterations, modifications, and improvements are intended to be part ofthis disclosure, and are intended to be within the spirit and scope ofthe invention. Accordingly, the foregoing description and drawings areby way of example only.

What is claimed is:
 1. A filter media comprising: a fiber web includinga plurality of glass fibers having a BaO content of greater than 7.2 wt% and an alumina content of less than 3.0 wt %.
 2. The filter media ofclaim 1, wherein the glass fibers have an average diameter of less than3 microns.
 3. The filter media of claim 1, wherein the glass fibers havea B₂O₃ content of between 5.0 wt % and 15.0 wt %.
 4. The filter media ofclaim 1, wherein the glass fibers have a B₂O₃ content of between 8.0 wt% and 15.0 wt %.
 5. The filter media of claim 1, wherein the BaO contentis less than 20.0 wt %.
 6. The filter media of claim 1, wherein the BaOcontent is between 8.0 wt % and 20.0 wt %.
 7. The filter media of claim1, wherein the glass fibers have an alumina content of between 0.5 wt %and 3.0 wt %.
 8. The filter media of claim 1, wherein the glass fibershave an alumina content of less than 2.5 wt %.
 9. The filter media ofclaim 1, wherein the glass fibers have an alumina content of between 1.0wt % and 2.5 wt %.
 10. The filter media of claim 1, wherein the glassfibers have a total alkali oxide content of between 10.0 wt % and 25.0wt %.
 11. The filter media of claim 1, wherein the glass fibers have aNa₂O content of between 6.0 wt % and 25.0 wt %.
 12. The filter media ofclaim 1, wherein the glass fibers have a K₂O content of between 0.5 wt %and 8.0 wt %.
 13. The filter media of claim 1, wherein the glass fibershave a total alkaline earth content of less than 20.0 wt %.
 14. Thefilter media of claim 1, wherein the glass fibers have a MgO content ofbetween 0.1 wt % and 8.0 wt %.
 15. The filter media of claim 1, whereinthe glass fibers have a CaO content of between 0.1 wt % and 15.0 wt %.16. The filter media of claim 1, wherein the glass fibers have a silicacontent of between 45.0 wt % and 80.0 wt %.
 17. The filter media ofclaim 1, wherein the glass fibers have a ZnO content of between 1.5 wt %and 8.0 wt %.
 18. The filter media of claim 1, wherein the fiber webexhibits a Kdis after 28 days of between 95 ng/hour/cm² and 200ng/hour/cm².
 19. The filter media of claim 1, wherein the glass fibershave an average diameter of greater than 0.1 micron.
 20. A filterelement comprising the filter media of claim
 19. 21. A filter mediacomprising: A fiber web including a plurality of glass fibers having aBaO content of greater than 7.2 wt %, an alumina content of less than10.0 wt % and a B₂O₃ content of greater than 5.0 wt %.